Convert characters to uppercase without using builtin funcins in CSharp.txt

using System;
using System.Collections.Generic;
using System.Text;
 
namespace LowerToUpper
{
   class LowerToUpper
   {
      public static String ConvertToUpperCase(String input)
      {
         String output = "";
         for (int i = 0; i < input.Length; i++)
         {
            if (input[i] >= 'a' && input[i] <= 'z')
            {
               output += (char)(input[i] - 'a' + 'A');
            }
            else
               output += input[i];
         }
         return output;
      }
 
      static void Main(string[] args)
      {
         System.Console.Write("Enter a string: ");
         String input = System.Console.ReadLine();
         input = ConvertToUpperCase(input);
         System.Console.WriteLine("Converted String in Upper Case: " + input);
      }
   }  
}
 
Enter a string: Software and Finance

Converted String in Upper Case: SOFTWARE AND FINANCE

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